ZFS Terminology

This section describes the basic terminology used throughout this book:

alternate boot environment

A boot environment that is created by the lucreate command
and possibly updated by the luupgrade command, but it is
not the active or primary boot environment. The alternate boot environment
can become the primary boot environment by running the luactivate command.

checksum

A 256-bit hash of the data in a file system block. The checksum
capability can range from the simple and fast fletcher4 (the default) to cryptographically
strong hashes such as SHA256.

clone

A file system whose initial contents are identical to the
contents of a snapshot.

A boot environment that is used by the lucreate command
to build the alternate boot environment. By default, the primary boot environment
is the current boot environment. This default can be overridden by using the lucreate-s option.

The process of copying data from one device to another device
is known as resilvering. For example, if a mirror device
is replaced or taken offline, the data from an up-to-date mirror device is
copied to the newly restored mirror device. This process is referred to as mirror resynchronization in traditional volume management products.